1. Field of the Invention
The present invention relates to a fire extinguishing composition comprising polyethyleneimine or a derivative thereof, and more particularly to a fire extinguishing composition which is superior in terms of rapid extinguishing performance, flame resistance, fuel resistance, and reignition prevention performance.
2. Description of the Background Art
Generally, in the case of fires involving polar solvents such as alcohols, ketones, esters, ethers and amines, even if fire extinguishing is attempted with a typical petroleum fire extinguishing composition, the foam disappears soon after contacting the combustion surface, and the fire is unable to be extinguished. As a result, the following types of compositions have been proposed as polar solvent fire extinguishing compositions:
(1) protein hydrolysates to which a metallic soap has been added,
(2) synthetic surfactants to which a metallic soap has been added,
(3) protein hydrolysates to which a fluorine based surfactant has been added (a fluorinated protein), and
(4) fluorine based surfactants to which a water soluble high molecular weight material has been added to form a thixotropic liquid.
Of these compositions, fire extinguishing compositions of type (4) above are aqueous film forming foam compositions based on a fluorine based surfactant, to which a water soluble high molecular weight material (such as a polysaccharide) has been added to give thixotropic properties. On contact with a polar solvent, foams which consist of this type of composition lose water at the combustion interface, and the remaining water soluble high molecular weight material, incorporating air bubbles, forms a gel-like mat across the solvent surface, preventing direct contact between the upper part of foam and the solvent, and covering the entire combustion surface. It is believed that the fire is then extinguished by cooling and smothering effects. Compared with the fire extinguishing compositions of types (1), (2) and (3) above, compositions of type (4) offer better foam development on the combustion surface, and also offer an improved fire extinguishing effect.
However, assuming the mechanism above, wherein the gel-like mat of the water soluble high molecular weight material protects the foam from the solvent, fire extinguishing compositions of the type (4) above will display poor fire extinguishing effect on solvents such as alcohols (such as isopropyl alcohol and t-butanol) or propylene oxide which have large heats of combustion or are highly volatile, and so depending on the type of solvent, the dilution ratio of the composition concentrate may need to be increased, which makes handling somewhat troublesome. Moreover, because fire extinguishing compositions of the type (4) described above rely on smothering utilizing the covering effect of the gel-like mat, good effects are displayed in so-called soft running methods where the foam is poured gently onto the surface of the fuel along the side wall of a tank such as in a foam chamber, but in methods where the foam is shot directly onto the solvent surface from the foam discharge nozzle of a chemical fire engine or the like, a method which represents the most common fire fighting strategy, the surface of the fuel is disturbed, meaning the gel-like mat can sink and the fuel surface can reappear above the mat and reignite, and consequently problems still remain over the performance of these type (4) compositions in actual fire fighting situations.
Furthermore, these fire extinguishing compositions incorporate large amounts of water soluble high molecular weight material, and so the composition concentrate is extremely viscous (at least 1200 mm2/s), and moreover the viscosity value varies considerably with temperature. Consequently, considerable care needs to be taken with the fire extinguishing equipment (such as mixers and piping), and there are handling concerns associated with the practical application of these types of compositions to existing equipment. Furthermore, conventionally these type of fire extinguishing compositions have been prone to forming a thin membrane (skin) on the surface of the liquid and on the walls of the tank during storage, and moreover producing sedimentation on the bottom of the tank, and problems have also arisen over the life of the product with concerns that they do not cope with extended storage. In addition, these types of fire extinguishing compositions also have a relatively high freezing point of approximately 0xc2x0 C., and because they are not reversible in terms of freezing and remelting, use or storage of such compositions in cold regions requires special considerations.
An example of a fire extinguishing composition which displays superior fuel resistance, flame resistance (for example, reignition sealing) and heat resistance when compared with conventional compositions was disclosed by the present applicants in Japanese Unexamined Patent Application, First Publication No. Sho-59-230566, and comprises a surfactant with an anionic hydrophilic group and a cationic water soluble high molecular weight compound, mixed with a third constituent comprising a polybasic acid compound of 3 to 24 carbon atoms.
However, although this fire extinguishing composition is able to be used for extinguishing both polar solvent fires and non-polar solvents, the time required to extinguish a fire is relatively long, and the composition could not be claimed to offer rapid fire extinguishing performance. In addition, the composition also has problems in terms of flame resistance, and reignition prevention. Furthermore, in actual fire fighting activity, when the fire extinguishing composition concentrate was diluted with either fresh water or sea water, problems arose in terms of the extended stability of the diluted solution, with cloudiness developing in the diluted solution.
An object of the present invention is to provide a fire extinguishing composition which when compared with conventional fire extinguishing compositions displays superior rapid fire extinguishing performance, flame resistance, fuel resistance and reignition prevention performance, for both non-polar solvent fires and polar solvent fires, as well as displaying superior stability as a diluted solution.
In order to achieve the above object, the present invention is a fire extinguishing composition which comprises a cationic polyamine based high molecular weight compound (A) which has primary, secondary, and tertiary cationic groups within the molecular structure and moreover in which the primary cationic groups account for no more than 40% by weight of the total cationic groups within the molecule.
The fire extinguishing composition of the present invention forms a foam which is extremely stable with respect to polar solvents, and yet also forms an aqueous film on the surface of non-polar solvents such as petroleum, and offers flame resistance and fuel resistance properties which display markedly improved rapid fire extinguishing performance and reignition prevention.